Direct fuel fired unit air heater



Nov. 2, 1948-- 1.. F. M CO NNELL 2,452,946

A I DIRECT FUEL FIRED UNIT AIR HEATER Filed June 14, 1945 2Sheets-Sheetl z I F/ z INVENTOR.

2 Sheets-Sheet 2 an m Nov. 2, 1948. L. F. M CONNELL DIRECT FUEL FIREDUNIT AIR HEATER Filed Jun 14, 1945 1N VEN TOR.

BY gum WZCM Patented Nov. 2, 1948 2,452,946 DIRECT FUEL FIRED UNIT AIRHEATER Leslie F. McConnell, Birmingham, Ala., assignor to McConnellSales and Engineering Corporation, a corporation of Alabama ApplicationJune 14, 1945, Serial No. 599,443

6 Claims.

My invention relates to a direct oil fired unit air heater forfurnishing comparatively low temperature heated air for drying, bakingand similar purposes where clean, smoke free, odor free and poisonousgas free, accurately controlled, warm or hot air is required.

In the drying of raw cotton. textiles food stuiis and similarcommodities emciently, it is necessary to remove the moisture content inthe material with heated air. In the drying of these materials in thepast, it has been necessary to use indirect fuel fired type heaters orsteam heaters for heating the air. These types of heaters areineflicient and the maintenance costs are high. There are direct oilfired unit heaters used on crude drying and baking ovens where smoke andgases are not detrimental to the processes, however, these have not beensatisfactory for the purposes listed above.

My invention is based on the principle of proper combustion of fuel oilin which complete combustion of the oil to CO2 and H20 occur only athigh temperatures and with proper fuel-air ratio. It is also based onthe principle that aldehydes or pungent gases can be formed in thecombustion of fuel oil if low temperature air cools the flame prior tocomplete combustion and my apparatus is designed to prevent the cool airfrom coming in contact with the flame before complete combustion takesplace.

The average unit air heater being used today requires a large space asdue to the principle of firing the combustion space necessary is basedon B. t. u. heat release per cubic foot of combustion space and 25,000to 50,000 E. t. u. is considered maximum. My invention utilizes theprinciple of combustion chamber flame capacity rather than thermalrelease of heat units and I am able to obtain at least 125,000 B. t. u.of fuel combustion per cubic foot of combustion space without affectingthe efficiency of the unit heater or the purity of the heated air withthe result that my invention requires a very small space.

My invention is illustrated more or less diagrammatically in theaccompanying drawings, wherein- Fig. 1 is a view in elevation showing myimproved heater;

Fig, 2 is a vertical cross section through the heater; and

Fig. 3 is a sectional plan view of the heater through the burner block.

Referring-to the drawings in which like reference numerals indicate thesame parts,

A is the outer hood.

2 B is the outer shell of the air heater.

C is the outlet air duct.

D are cast or pipe supports for the angleE which partially supports thecast grating H which in turn support the combustion chamber.

E is a circular shaped angle welded to the supports D for partiallysupporting the cast grating.

G is a circular shaped angle welded to the outer shell for supportingthe cast grating.

H are cast grating areas for supporting the refractories. This could bea solid plate, however, I have foundcast grating to be superior.

J is a, rammed plastic refractory used to save installation costs. It isunderstood that refractory shapes could be used if desired.

K is a refractory or alloy cylinder either solid or sectional the heightof which is variable depending on the flame capacity required.

L is a refractory brick or plastic lining.

M is an outer lining of insulating or soft refractory material to allowprovision for expansion of the refractory lining.

N is a superrefractory material used to withstand the fiame impingementadjacent to the burner.

0 is the refractory burner block that can be adjusted as to locationeither vertically or horizontally in order to obtain proper combustionto meet variable conditions and to give a centrifugal movement of thecombustion flame.

It is understood that any number of burners and burner blocks can beused if desired. It is also understood that the burner block is part ofthe fuel burner used with this unit heater and although the burner orburners are not shown in the drawing the burner block diagrammaticallyrepresents the burners used. These burners may be either manually orautomatically ignited.

P is a cast or fabricated inner hood having ribs or vanes to both impartadditional heating to the incoming air by providing greater contactsurface and to also direct the incoming air in a centrifugal flowcounter current to that of the centrifugal flow of the combustion flame,

Q is the counterbalanced damper in the vent stack.

R is the vent stack.

S is the counterbalance for the stack damper.

In the operation of my invention, an exhaust fan connected to the outletC pulls the air to be heated through the air heater. The burner orburners are either manually controlled or automatically controlled toregulate the temperature of the heated air. The unit air heater can becompletely equipped with safety devices to prevent explosions,incomplete combustion, venting of the heater before lighting. A solenoidshut off valve is located in the fuel line which in turn is wiredthrough the combustion air fan, which delivers air through the burnerblock 0, so that fuel cannot be supplied to the unit unless thecombustion air is supplied to the burner. An air flow switch is'l'ocatedinthe exhaust duct which is also wired through the fuel line shut offvalve so that no fuel can be sup lied to the air heater unless air isbeing pulled through the unit heater. A flame protection device canbesup-plied to close off all fuel in the event of flame failure.

From the foregoing, it willbes'een thatIhave provided a direct fuelfired unit heater in which the outside of the central air ducti's hotterthan the inside thereof, thereby resulting in longer life. In a circularrefractory or alloy shape, the" outer circumference of the shape isproportionally greater than the inner circumference.- As the coefiicientof expansion of themater'ial'is a constant, if the inside wall can-bekept at a; lower temperature than the outside, as is the case with myinvention, there is a decided freedom from cracking. Where thecombustion chamber is in the center and'the airiso'n the outside as isthe case' with'- conventional air heaters, there'- is a highertemperature on the inside and a lower temperature on the'out'side' whichcauses serious cracking due to the fact that the outer circumferencedoes not-expand in proportion' tothe inner circumference.

.r claim:

1. In a furnace of thecharacter described, a circular wall forming acombustion chamber, a circular duct disposed concentrically within thecombustion chamberand spaced from the walls thereof, said combustionchamber having an'inlet opening at oneend'for air to be heated'inalignmentwith the circular duct; means in the inlet opening to impartcentrifugal movement to the" air, and a fuel burnerdisposedt'angentially of the combustion chamber at the other endthereofthrough the combustion chamber wall, and dis posedto iinpartacentrifugal 'movement to the products of combustion in animation-counterto bustion chamberhaving. a cylindrical outer shell;-

chamber, open at its upper end and having an outlet at its lower end forcommingled air and products of combustion, and a hood over thecomb-ustion chamber and duct having a skirt extending downwardly inspaced relation around the combustion chamber to provide an air inletinto the combustion chamber. 1

4L An'air' heating furnace comprising a vertical- 13 disposedcylindrical combustion chamber, means to introduce products ofcombustion tangentially into the lower end of the combustion chamber atone end thereof, a cylindrical duct disposed concentrically within thecombustion chamber, open at it'supper end and having an outlet at itslower" end for commingled air and products 'of'combustion, and a hoodover the combustion chamber and duct having a skirt extending downwardlyin spaced relation around the combustion chamber to provide an air inletinto the combustion chamber, and means to impart a whirling motion tothe air entering the duct.-

5. In an air heating furnace, an outer cylin dric'al shell having anopening in its bottom, an open: ended inner cylindrical shell of lessdiameter and length than the outer shell fitting-at its lower end insaid opening, a cover for the outer shell spaced above the open upperend of the inner shell and having an air' passage in align ment With theopening in said innershell, a burner positioned between said inner andouter hells adjacent'the bottomsthereof, and'me'ans to drawair-downwardly through-the inner shell.

6. man ai'r heating furnace, an outer'cyli-ndr'ical shell'of refractorymaterial having a bottom and a cover} a centrally open cylindrical shellof refractory material of less diameter and length than-the"outershell-over said bottom'opening}. a fuel burner adjacent'the bottoms'ofsaid cylindrical shells and disposed to discharge tangentiallytherebetween, a" hood'over the top'ofthe outer shell having a dependingskirtspaced-from the'walls-of theo'u-tershell, there being a ceii'trall'y disposed openin'g in said cover over the in ner shellgand mean'sto draw air into saidhood and downwardly throughthe inriefshell.

LESLIE F. MCCONNELL.-

REFERENCES CITED" fhe following references are of" recordin the file ofthis patent: V

UNITED STATES PATENTS France' uri July 24 1-939

